1. Field of the Invention
The invention relates to light curing of resins used to fill teeth and bond porcelain veneers and fillings to teeth. In particular, the method and apparatus of the invention relate to determining the curing characteristics of such resins.
2. Related Art
The state of the art in dental materials involves the use of light cured resins to fill teeth and to bond porcelain veneers and fillings to teeth. Curing these materials requires the use of a high intensity light that causes the resin to harden. Curing times are in the range of 20 or more seconds, depending on the thickness and translucency of the resin and the intensity of the light. These factors are not easily measurable or always constant. The intensity of curing lights can vary from manufacturer to manufacturer and may not be constant over time. For example, the light may deteriorate over time, depending on the bulb, internal light filter and fiber optics.
Depth of cure is important information for a dentist to know. The depth of cure determines how long a light needs to be held over a restoration to assure complete hardening to the bottom where it bonds to the tooth. Since this can vary from 20 seconds to more than a minute, a dentist cannot be certain at any point and time if the material has completely cured. Removal of the curing light prior to complete curing of the resin invites failure of the restoration. On the other hand, excessively long curing is an inefficient use of time which ultimately results in higher cost to patients. In addition, it is not possible for a dentist to determine if the efficiency or effectiveness of a curing light is diminishing over time. Thus, the dentist could be unaware that a previously adequate curing duration may have become inadequate as a result of diminishing efficacy of the curing light. This further reduces the chances of clinical success of a filling or bonding.
To date, there has been no convenient means of determining depth of cure of resins used in dental restorations. Due to the importance of this information for effective dental restorations it is desirable to have an apparatus for checking resin cure characteristics before the resin is used to fill a restoration cavity. U.S. Pat. No. 3,295,208 to Redtenbacher discloses an apparatus for determining the working length of root canal instruments. While Redtenbacher discloses the use of a box in the dental field to establish the working length of a particular instrument, it does not disclose of use such a box for calibrating the depth of cure of a resin.
U.S. Pat. No. 4,505,675 to Albert discloses a method and device for preparing an endodontic filler. While Albert '675 discloses the use a calibrated cavity for preparing material for filling a tooth, it to fails to disclose the use a hinged box for determining the cure of a resin to be used in filling a tooth.
U.S. Pat. No. 1,857,289 to Schwartz discloses an arrangement for making dental molds. However, there is no disclosure of checking the curing of a resin using calibrated cavities.
Finally, U.S. Pat. No. 3,815,851 to Girard discloses a mold for casting test samples but also fails to disclose use of a plurality of calibrated cavities to reveal the depth of cure.